Category: Molecular Vapour Deposition

Nexus has been examining a new, novel technique that may be able to superior protection for electronic circuit boards compared to the standard coating methods like conformal coatings and Parylene but also actually be cost-effective.

So, why is this new coating so good compared to Parylene and other conformal coatings?

The final MVD coating built up is much thinner than the other traditional coatings including Parylene. However, its protective performance has been found to be superior to them all in most categories of testing so far.

Key performance indicators like Water Vapor Transmission Rate (WVTR), optical clarity, temperature resistance and hydrophobicity have been found to be much better than the other coatings.

Further, the really exciting part about this technology is the cost of processing that is extremely low.

Since the coating is extremely thin then it has been found that no masking is required. This is because when components like connectors are joined together then the ultrathin coating does not prevent electrical connection.

This means that the cost of process is purely the cost of application of the material and nothing else.

Since the process is relatively low cost then this does offer a very interesting alternative to the traditional coating materials.

So what does the science of Molecular Vapor Deposition coating (MVD) look like?

The actual film is built up of alternating layers of ALD and CVD thin coating layers.

The ALD is a ceramic-based material providing the insulating properties. The CVD film provides the barrier protection.

First, an ALD layer is applied to the substrate. Then a CVD layer is applied. Then a further ALD layer is applied and so on.

This continues until the correct number of layers is built that has the right protection.

Finally, once the required film thickness is achieved with the alternating layers, then a final hydrophobic thin film layer is applied, that combines with the ALD and CVD layers to provide a highly effective barrier.

So, just how good is the hybrid coating as a protective material for electronic circuit boards?

Generally, with protective coatings for electronics then Parylene is considered the gold standard in most cases.

So, Nexus compared Parylene with the MVD material.

Property

Parylene

MVD Coating

Hardness

Soft

Hard

Wear resistance/Handling Ease

Poor

Excellent

Water Vapor Transmission Rate

Good

Excellent

Temperature Resistance (extended time)

100°C

350°C

Color

Gray/white

Clear

Adhesion to various materials

Poor

Excellent

Scalable to large production

Poor

Excellent

Process Time

8 – 12 hrs

8 – 12 hrs

Hydrophobicity

Good

Good – Excellent

Cost

High

Low – Med

What Nexus also identified for the material were some key properties.

The Water Vapor Transmission Rate (WVTR) is superior to Parylene so the coating is far more waterproof.

Coating adhesion is superior as it covalently bonds to the substrate. So, the lifetime of the material will be better on the circuit.

The temperature range of the material can be up to 350C without any degradation.

The hybrid coating is UV stable whereas Parylene in general is not. This is an important criteria for coatings exposed to UV light.

The coating stayed 100% transparent during testing (no loss of lux).

The coating thickness of the hybrid material is x10 LESS than the Parylene. This aids light transmission and electric connectivity

So, in reality the MVD material could just be what industries like the automotive and LED sectors are looking for in protecting their circuits where cost and protection abilities are critical.

The final coating built up is much thinner than the other traditional coatings including Parylene. However, its protective performance has been found to be superior to them all in most categories of testing so far.

Further, the really exciting part about this technology is the cost of processing.

Since the coating is extremely thin then it has been found that no masking is required.

This is because when components like connectors are joined together then the ultrathin coating does not prevent electrical connection. Even better, the physical protection is not compromised.

This means that the cost of process is purely the cost of application of the material and nothing else.

Since the process is relatively low cost then this does offer a very interesting alternative to the traditional coating materials.

Does MVD sound complex?

Actually, although the technology and chemistry can be a little complex the process itself is fairly simple.

Once the process is set up in the machine the operator just loads, switches the machine on and unloads on completion.

This is a far cry from the sophisticated processes of robotic selective coating or the challenges of Parylene. Further, the process is actually very stable and in reality is tried and test in other industries.

So what does a MVD film look like?

The film is built up of alternating layers of ALD and CVD thin coating layers. The ALD is a ceramic-based material providing the insulating properties and the CVD film provides the barrier protection.

Once the required film thickness is achieved then a final hydrophobic layer is applied that combines with the ALD and CVD layers to provide a highly effective barrier.

Label: The film is built up of alternating layers of ALD and CVD thin coating layers. The ALD is a ceramic-based material and the CVD film is an organic layer.

So how well did the MVD coating perform when protecting circuit boards?

Data was recently presented at Apex in Sand Diego looking at live LED circuits from a customer.

The customer LED product was for outdoor application. For testing, the customer used in-house test methods to prove the technology.

The LED circuit was exposed to customer tests for resistance against salt, moisture and temperature.

The test methods included:

Initial test submerged in DI water dip for 12 hours

Second test submerged in 25% concentration saltwater dip for 17 hours

Third test 2 x 6 hour cycles in water ramped from room temperature to 70°C

After each test the boards were tested for failure or problems.

The LED circuit passed on all tests. All results achieved were completed with no masking of components and zero light loss in LED opacity.

The electrical connections were found to be excellent and the coating did not affect the integrity of the connectors.

So what about the cost of process for MVD?

Since the process is masking and de-masking free then the cost per unit is incredibly low. The performance is also superior to nearly all the traditional methods of coating protection.

Further, the protective properties of the MVD coating in nearly all cases is superior to the conventional methods.

So, you get a lower cost coating with a higher technical performance.

So, just how good is the MVD coating as a protective material for electronics?

Generally, with protective coatings for electronics then Parylene is considered the gold standard in most cases.

So, we compared Parylene with the MVD coating material.

Property

Parylene

MVD

Hardness

Soft

Hard

Wear resistance/Handling Ease

Poor

Excellent

Water Vapor Transmission Rate

Good

Excellent

Temperature Resistance (extended time)

100°C

350°C

Color

Gray/white

Clear

Adhesion to various materials

Poor

Excellent

Scalable to large production

Poor

Excellent

Process Time

8 – 12 hrs

8 – 12 hrs

Hydrophobicity

Good

Good – Excellent

Cost

High

Low – Med

What we also identified for the material were some key properties for LEDs.

The Water Vapor Transmission Rate (WVTR) is superior to Parylene so the coating is far more waterproof for the LEDs

Coating adhesion is superior as it covalently bonds to the substrate. So, the lifetime of the material will be better on the circuit.

The hybrid coating is UV stable whereas Parylene in general is not. This is an important criteria for coatings exposed outside on LEDs

The coating stayed 100% transparent during testing (no loss of lux). That again is important for LEDs.

The coating thickness of the hybrid material is x10 LESS than the Parylene. This aids light transmission and electric connectivity

So, in reality the MVD material could just be what the high volume electronics industry is looking for in protecting their circuits.

Need to find out more?

For further information on Molecular Vapour Deposition (MVD) then contact us directly.

Anti-fouling and lubrication coatings for parts implanted in the human eye

Dielectric films used in virtual reality displays

Release layers for nano-imprint lithography

MVD is used in many different modern day electronics

What are the advantages of MVD

Complete coverage

The MVD process is designed to produce 100% coverage of all exposed surfaces on complex parts.

Conformal coating thickness control

The MVD process manages film thickness and thickness uniformity by dosing exact amounts of precursors and controlling reaction times.

Many other processes like Parylene are dependent upon amount of dimer and will continue to deposit successive polymer layers until it is completely used up causing thickness variation across the chamber.

Cost of process

MVD does appear to be a much faster process compared to Parylene to create like for like protection.

Also, it does not require silane pre-treatment and it only requires small amounts of chemicals. As a result, PCB processing cost could be very low compared to Parylene.